1. Technical Field
The present invention relates to methods for controlling an electro-optic device, devices for controlling an electro-optic device, electro-optic devices, and electronic apparatuses.
2. Related Art
An electrophoretic display device is one example of the electro-optical devices described above. The electrophoretic display device displays images at a display section by applying voltages between pixel electrodes and an opposing counter electrode with electrophoretic elements containing electrophoretic particles sandwiched therebetween, thereby migrating electrophoretic particles, such as, black particles and white particles. The electrophoretic elements are composed of a plurality of microcapsules each containing a plurality of electrophoretic particles, and affixed between the pixel electrodes and the counter electrode with an adhesive composed of resin or the like. Note that the counter electrode may also be called a common electrode.
With such an electrophoretic display device, for example, white color can be displayed by applying a voltage that moves white particles to the display surface side, and black color can be display by applying voltage that moves black particles to the display surface side. Also, by adjusting the period for applying the voltage for white color or black color described above, an intermediate gray level between white color and black color (in other words, gray color) can be displayed (see, for example, U.S. Published Patent Application 2005/0001812 (Patent Document 1), U.S. Published Patent Application 2005/0280626 (Patent Document 2) and WIPO Published Patent Application WO/2005/101363 (Patent Document 3)).
For displaying the intermediate gray level, each of the particles may only have to be moved to the middle position between white and black displays. However, such a control is difficult, and variations might be generated in the gray level to be displayed because, for example, differences occur in the positions of the respective particles. In particular, when plural intermediate gray levels are to be displayed, the variations described above greatly impact on the display image.
In contrast, for example, when the gray level is changed from light gray (that is, gray color close to white) to dark gray (that is, gray color close to black), each particle may be once moved to the position for displaying the white color or the black color from the state where the light gray is displayed, and then moved to the position for displaying the dark gray. As a result, the positions of the particles for each of the pixels can be made uniform and the intermediate gray level can be suitably displayed.
However, as described above, when voltages of mutually different polarities are alternately impressed for rewriting, bias may be caused in the polarities of the voltages impressed to the pixels through the overall rewriting process. Concretely, a difference may occur between the period in which the voltage with a polarity corresponding to white is impressed and the period in which the voltage with a polarity corresponding to black is impressed.
According to the research conducted by the inventor, if such bias is caused in the polarities as described above, it has been found that troubles, such as, for example, image burn-in and deterioration of the display section may occur. However, the technical documents of related art described above do not refer to the bias in polarities at all. In other words, the related art including the technical documents described above has a technical problem in that generation of bias in the polarities to be impressed to pixels cannot be prevented.